More than 100 leading figures of literature, film and academia in India rallied this weekend against a "colonial-era" law making homosexuality a criminal offence.

In an open letter, more than 100 influential signatories, including the Nobel laureate economist Amartya Sen, the Booker prizewinner Arundhati Roy, and author Vikram Seth, said the law had been used to "systematically persecute, blackmail, arrest and terrorise sexual minorities" and had spawned intolerance.

They argued that section 377 of the Indian penal code perpetuated Victorian-era antipathy and bigotry towards gay people. "This is why we ... support the overturning of [the law that criminalises] romantic love and private, consensual acts between adults of the same sex," they said.

The legislation, which came into effect during British rule in India, bans "carnal intercourse against the order of nature with any man, woman or animal".

Vikram Seth, the author of the best-sellers A Suitable Boy and An Equal Music, told a television channel: "The reason why I decided I would participate in this is that I am gay, or at least partially gay."

Seth, whose writing has encompassed homosexuality, said India's population of more than 1 billion people meant the law affected vast numbers. "We cannot suppress the happiness of 50 or 100 million people," he told NDTV.

Discrimination against homosexuals is widespread. Earlier this year the heir of a former royal family was disinherited after saying he was gay. There have been many reports of lesbians forcibly separated.

Campaigners have lodged a petition with the high court in Delhi challenging the law. This will be heard next month. However, the government has already told supreme court judges that public opinion is not in favour of a change.

One of India's best-known television journalists, Rajdeep Sardesai, who is a signatory to the protest letter, said: "Despite the sexual revolution taking place in India, and the fact we are modern in many ways, there is a deep conservatism at work here. Until sexuality is debated in the public sphere we will have these laws."

The letter has also won backing from across the political spectrum with support from a former attorney general and a powerful Hindu priest, Swami Agnivesh. The campaign got a recent boost when the official HIV/Aids control agency said the law made it harder to check the spread of the virus in India, which has the world's highest number of infected people.